1. Field of the Invention
The present invention relates to a pitch lock system for a wind turbine with a rotor, said rotor comprising at least one pitchable blade, said at least one blade being a traditional pitch blade connected to said rotor at a interface or being at least one partial pitch blade, said at least one partial pitch blade comprising a outer blade part and a inner blade part, where said blade parts are interconnected at a interface, said interface comprising a pitch bearing construction with a first bearing ring and a second bearing ring, for pitching at least a part of said blade in relation to said rotor, wherein the pitch lock system comprises a movable toothed segment for interacting with at least one toothed element, where said toothed segment is slideably connected with one of the first or the second bearing ring, and where said toothed element is in fixed connection with the other of the first or second bearing ring, and where the pitch lock system further comprises an actuator for activating and sliding/moving said movable toothed segment in a direction parallel to a radial direction of the bearing ring and into engagement with said toothed element and thus locking the pitch bearing construction.
2. Background of the Invention
It is well known that wind turbines have some kind of brake or lock system for braking and/or locking the rotor of the turbine in a specific position during repair work or other situations where there is a need for a secure stand still of the rotor. Also systems for locking the individual blades of a wind turbine in specific positions are known.
DE 10 2004 017 323 A1 teach a solution to the problem with slack and wear between the parts that are used for pitching a blade for a wind turbine into certain positions. The problem can be solved by using some kind of locking mechanism e.g. a bolt that is placed in a corresponding hole or by having some kind of brake mechanism build into the pitch bearing. Such a brake system can be a disc brake, a magnet brake or a drum brake. By using a bolt lock mechanism a very simple solution is obtained, but the blade can only be locked in predetermined positions and thus the solution is somewhat static. By using a brake system, the possibility to position the blade in a very specific position is possible, but installing a brake system is a rather complex job and further the system can not provide a foolproof locking of the blade.
US 2011/0044813 A1 also shows a pitch lock mechanism, for locking the pitch bearing system in a fixed position, but this system has the disadvantage that the pitch bearing only can be locked in one or more specific positions, which does not allow for dynamic and free choice of locking position. This system has the same drawbacks as the system discussed above.
EP 1 167 754 A2 concerns a locking mechanism for a wind turbine rotor, where the locking mechanism is integrated into a disc brake system. In one embodiment of the system, the disc is locked in a fixed position by a toothed segment, and in another embodiment the disc can be turned by the locking parts.
A brake or lock system for a pitch bearing construction on a wind turbine is normally arranged between the outer ring and the inner ring of a pitch bearing, which typically is a ball bearing. The outer ring will often be fixed to the hub of a wind turbine and the inner ring will be fixed to the blade. The blade will thus be able to be pitched—turned—in a longitudinal direction of the blade. This movement will often be facilitated by an electro motor and a gear unit or by a hydraulic unit. The unit will normally be acting with a sprocket on a toothed element on the inner ring of said bearing. The pitch bearing construction can be held in a given position, but at the interface between the sprocket and the toothed element is the teeth of the parts; there will always be some slack between the parts. Further the unit cannot provide a safe and secure mechanical locking of the pitch bearing construction.
As the above mentioned solutions the solution in EP 1 167 754 A2 is also designed to block a turning movement at certain specific positions. This can in one embodiment be done by pushing a toothed brake block into engagement with a toothed element on the slewing ring. It is however only possible to engage the brake block when it is aligned with the teeth on the toothed element. In other words the brake will only work if and when a full alignment of the two parts has taken place. Especially during repair work this is not always possible. If a pitch gear is blocked and has to be repaired or replaced it is very important to be able to perform a full locking of the inner ring in relation to the outer ring, before doing any work at the pitch bearing. This is not possible with any of the above mentioned solutions and thus a number of straps, pulleys and other tools must be taken in action, which is very time consuming an still does not provide a secure locking of the various parts.
None of the above mentioned systems show a pitch lock system for a wind turbine that solves the problem of preventing slack in the system and at the same time being a sturdy and robust locking system, comprising a mechanical lock, where the locking position is completely individual, meaning that the pitch bearing construction can be locked in every possible position.